Evaluation in virtual reality of a master switch with an emergency stop for elevating work platforms

Status:

completed 08/2013

Aims:

Efforts made in the past to prevent accidents during the operation of elevating work platforms have contributed to stabilization of the accident statistics, despite elevating work platforms being used increasingly in greater numbers in a broader range of areas. However, accidents in which the operator is crushed between the platform and surrounding elements (such as ceiling beams), for example owing to selection of an inappropriate direction of movement, are particularly common. Various activities and initiatives conducted by the German Social Accident Insurance Institutions have resulted in new technical design solutions intended to prevent accidents in the future and to enhance safety during work with elevating work platforms. Evaluation of the usability of innovative safety products during the earliest possible phases of product development but nevertheless with consideration for the circumstances of their future context of use can contribute to prevention activity being effective on a wide scale and from an early stage. For this reason, the Subcommittee Transportation, Storage, Logistics in Goods Handling of the DGUV's Expert Committee Trade and Logistics has, with the support of the German Social Accident Insurance Institutions for the woodworking and metalworking industries (BGHM) and the trade and distribution industries (BGHW), launched a research project at the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA). The usability of a supplementary protective measure for elevating work platforms in the form of an emergency-stop function (cf. IFA information sheet 0332) was to be evaluated in virtual reality (VR). Hazardous situations in the context of use of the emergency stop should be of particular interest.

Activities/Methods:

Literature surveys were conducted in the first instance in order to obtain information on the context of use of elevating work platforms, on hazards and accidents, and on possible causes and measures for intervention. For the purpose of a preliminary simulation study, a VR model was developed for the operation of elevating work platforms by a worker in a virtual work scenario. This study, conducted in the IFA's SUTAVE laboratory, also had the function of integrating data logging into the VR model. Some of the data proved useful for evaluation of the driver and work performance, and were supplemented intelligently during the study by other psychophysiological dimensions and surveys.

For the subsequent simulation study for evaluation of the usability of an emergency-stop function within the master switch, a complex work scenario was simulated in a storage depot with a steel ceiling construction. In reality the fenced platform of an elevating work platform including control unit was also placed in the laboratory and integrated into the VR model. Finally, further modifications were made to the elevating work platform in order to make task performance within the work scenario more realistic. For this purpose, the master switch for control of the elevating work platform was equipped with the emergency-stop function (cf. IFA information sheet 0332 (PDF, 173 kB, non-accessible) ), and various adjustment stages were defined for the actuating force of the emergency stop. The force for actuation of the function was varied systematically in the study. 20 participants performed several sessions comprising inspection and driving tasks in the IFA's SUTAVE laboratory. In addition to task performance, psychophysiological measures were continuously recorded and operator ratings were taken for workload and usability.

Results:

Analysis of the preliminary simulation study showed that an elevating work platform can be used with a high degree of realism in our VR environment. Both the driving track and the operator behaviour are essentially comparable with those of a real environment.

Overall, the results of the second simulation study show that the supplementary protective measure is used for initiation of the emergency-stop function less frequently (intentionally in the presence of a hazard and unintentionally in the absence of a hazard) when force exertion is high and more frequently when force exertion is low. In addition, it was evident that this protective measure can prove effective in practical use in the field, provided consideration is given to various requirements concerning the control of the elevating work platform and the design of the protective measure. This concerns for example the selection and implementation of the control mode in the master switch, and the specifications for reasonable force exertion for initiation of the stop function.

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